Motor vehicle fuel systems

ABSTRACT

System for preventing loss of vapors from a motor vehicle fuel system comprising a filter bed and connections to said bed from the carburetor float chamber and fuel tank, said filter being permanently vented through the air cleaner, and vented to the choke region of the carburetor whenever the engine is delivering more than a predetermined amount of power.

United States Patent [72] Inventors PeterP.Swatman Olton, Solihull;

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tions to said bed from the carburetor float chamber and fuel tank, saidfilter being permanently vented through the air cleaner, and vented tothe choke region of the carburetor whenever the engine is deliveringmore than a predetermined a umw w 1 l 5 Mom-M2 u m H 2 0 l 2 l 0 mh c .Im I C mm IF m um uoooonooou (ooceooouno MOTOR VEHICLE FUEL SYSTEMS Thisinvention relates to motor vehicle fuel systems of the kind in which aliquid-fuel tank, mounted on the vehicle, is arranged to supply fuel tothe float chamber of a carburetor of the controllable jet, automaticvariable-choke type having a fuel-metering jet controlled by a contouredmetering needle in dependence upon the instantaneous position of asuctionoperated piston that controls the effective cross-sectional areaof a choke in the main air passage of the carburetor.

The aim of the invention is to obviate, as far as possible, atmosphericpollution which is ordinarily caused by uncontrolled evaporative loss offuel from a motor vehicle fuel system of the kind specified. To thisend, according to the invention, the fuel tank and the carburetor floatchamber are sealed to preclude uncontrolled evaporative loss of fuel,and the fuel vapor produced from them is trapped in a canistercontaining a bed of activated granular charcoal which adsorbs the fuelvapor; permanent communication is established between the usual engineair cleaner and the top of the canister; and from the base of thecanister a connecting pipe leads to an outlet located in the carburetorbody adjacent to the choke, this outlet being obturated by thesuction-operated piston whenever the engine of the vehicle is operatingunder the smaller power output conditions of any legislatively imposedatmospheric pollution test cycle, but whenever the engine is operatingat conditions requiring a greater power output, the outlet becomesuncovered by the piston with the result that purging of the canisterthen takes place by reason of the adsorbed fuel being entrained by theinduced air flow and being discharged into the choke region of thecarburetor.

The respective vapor spaces of the fuel tank and the carburetor floatchamber are connected by piping to perforated rings which are disposedat the top of the charcoal bed inside the canister.

The above-mentioned outlet, for purging the canister, is located at sucha height above the usual bridge member in the main air passage of thecarburetor that it remains obturated by the smaller-diameter portion(i.e. the shank) of the suctionoperated piston until the flow of airthrough the main air passage is sufficiently great to cause the pistonto be lifted to such an extent that the purge outlet becomes uncovered.

The accompanying drawing illustrates schematically a motor vehicle fuelsystem incorporating the invention. In this system a carburetor l of thecontrollable jet, automatic variable-choke type has a fuel-metering jet2 controlled by a contoured metering needle 3 in dependence upon theinstantaneous position of a suction-operated piston 4 which is locatedin a suction chamber 5. The piston 4 also controls the effectivecross-sectional area of a choke 6 established, as usual, between thebase of the piston and a bridge member 7 which contains the jet 2, thechoke 6 being in the main air passage of the carburetor. Although thisis not shown in the schematic drawing, a disc-type throttle valve is, asusual, located downstream of the jet 2.

When the carburetor l is in operation, the suction exerted in thesubstantially constant depression region (lying between the choke 6 andthe throttle valve) causes the jet 2 to discharge liquid fuel drawn froma float chamber 8, by way of a pipe 9 and a jet assembly 10. The supplyof liquid fuel to the float chamber 8, through a pipe 11 connected to afuel tank 12. is controlled in the usual manner by a float needle 13.

What has so far been described with reference to the drawing pertains tothe construction and operation of a well-known design of carburetor.

In accordance with the invention the fuel tank 12 and the carburetorfloat chamber 8 are sealed to preclude uncontrolled evaporative loss offuel, and the fuel vapor produced from them is trapped in a canister 14containing a bed of activated granular charcoal (not shown) whichadsorbs the fuel vapor. To this end, the respective vapor spaces of thefuel tank 12 and the carburetor float chamber 8 are connected, by pipes15 and 16 respectively, to corresponding perforated rings 15A and 16Adisposed horizontally at the top of the charcoal bed.

By way of a pipe 17, permanent communication is established between theusual engine air cleaner (not shown) and the top of the charcoalcanister 14.

From the base of the charcoal canister 14 a connecting pipe 18 leads toan outlet 19 located in the carburetor body adjacent to the choke 6.This outlet 19 is obturated by the shank of the suction-operated piston4 whenever the engine of the vehicle is operating under the smallerpower output conditions of any legislatively imposed atmosphericpollution test cycle (such as the so-called California cycle). Butwhenever the engine is operating at conditions requiring a greater poweroutput, the outlet 19 becomes uncovered by the shank of the piston 4.Purging of the charcoal canister 14 then takes place by reason of theadsorbed fuel being entrained by the induced air flow and beingdischarged, from the outlet 19, into the choke region of the carburetor.

We claim:

1. A motor vehicle fuel system comprising a fuel tank and a carburetorhaving a float chamber and a suctionoperated piston which controls thearea of the choke opening, both said fuel tank and said float chamberbeing sealed to preclude uncontrolled evaporative loss of fuel andconnected through permanently open vent means to a canister containing abed of material which adsorbs the fuel vapor; an air cleaner permanentlyconnected to the top of the canister; and a connecting pipe leading fromthe base of said canister to an outlet so positioned in the carburetorbody as to be obturated by said suction-operated piston whenever theengine of the vehicle is operating under the smaller output conditionsof its operating range, but uncovered by said suction-operated pistonwhenever the engine is operating at conditions requiring a greater poweroutput, whereby said canister is purged by suction of the fuel adsorbedtherein through said connecting pipe and outlet into the choke region ofthe carburetor.

2. A system as claimed in claim 1 in which said bed of material is a bedof activated granular charcoal.

3. A motor vehicle fuel system according to claim 1, in which therespective vapor spaces of the fuel tank and the car buretor floatchamber are connected by piping to perforated rings which are disposedat the top of the charcoal bed inside the canister.

1. A motor vehicle fuel system comprising a fuel tank and a carburetorhaving a float chamber and a suction-operated piston which controls thearea of the choke opening, both said fuel tank and said float chamberbeing sealed to preclude uncontrolled evaporative loss of fuel andconnected through permanently open vent means to a canister containing abed of material which adsorbs the fuel vapor; an air cleaner permanentlyconnected to the top of the canister; and a connecting pipe leading fromthe base of said canister to an outlet so positioned in the carburetorbody as to be obturated by said suction-operated piston whenever theengine of the vehicle is operating under the smaller output conditionsof its operating range, but uncovered by said suction-operated pistonwhenever the engine is operating at conditions requiring a greater poweroutput, whereby said canister is purged by suction of the fuel adsorbedtherein through said connecting pipe and outlet into the choke region ofthe carburetor.
 2. A system as claimed in claim 1 in which said bed ofmaterial is a bed of activated granular charcoal.
 3. A motor vehiclefuel system according to claim 1, in which the respective vapor spacesof the fuel tank and the carburetor float chamber are connected bypiping to perforated rings which are disposed at the top of the charcoalbed inside the canister.